Biocidal plastic material

ABSTRACT

A plastics material comprises an acrylic polymer containing 5-50% of a rubbery copolymer and a biocidal compound. The plastic material is useful as a component of a refrigerator, worktop etc. or as a building material. The material may be used as a coating for a substrate. Method of manufacturing laminate materials comprising the plastics material are also claimed.

The present invention relates to plastics materials, in particular toplastics which are resistant to the growth of certain microbiologicalspecies, such as fungi or bacteria.

Plastics materials are very commonly used in the manufacture of a widevariety of articles such as refrigerators, worktops, shelves etc. Thesearticles may be likely to come into contact with biological specieswhich are harmful to health and which may spread and grow upon thesurface of the article. The control of harmful microbes is alsodesirable in certain medical applications when the growth of bacteriaetc. on benchtops, trays etc. is to be prevented. The incorporation of abiocidal compound into the plastics used in such applications maytherefore provide beneficial effects in that the growth of bacteria orfungi on the lining of a fridge, for example, may be inhibited.

Certain polymeric materials, e.g. polyvinylchloride, are susceptible tobiological attack, especially from fungi. In order to reduce or preventthe degradation of plastics resulting from such biological attack,biocidal products have been developed for incorporation into plasticsmaterials or paints to kill the fungi or bacteria responsible or preventtheir proliferation. It is also known to incorporate biocidal compoundsinto plastics to prevent the growth of bacteria or fungi found in foodproducts. Examples of the latter type of product are described in U.S.Pat. No. 5,433,424, JP-A-06287403 and JP-A-07071 869 amongst others, andarticles such as food-praparation surfaces and household food containersetc are already widely available to consumers.

WO-96/29361 describes a biocidal polymeric matrix comprising a supportmatrix, an antimicrobial agent and a carrying agent, wherein thecarrying agent and the antimicrobial agent are adapted to form at leastone hydrogen bond or salt bridge therebetween.

WO 96135205 describes a white cover for piano keys formed by injectionmoulding a homogeneous dispersion of a methyl methacrylate resin and0.5-2% of an antibacterial agent comprising a ceramic body prepared bysintering and mixing calcium phosphate and metallic silver.

WO 98/21253 describes polymers which have antimicrobial propertiesconsisting of copolymers of non-functional vinyl monomers with vinylcomonomers of specified composition having ionic functionality.

WO 96/22023 describes the use of 2-alkyl or 2-aralkylbenzisothiazolin-3-one derivatives as fungicides for plastics materials.

JP-A-08257493 describes the use of a steel plate which has a paintcoating incorporating inorganic aggregates containing anti-bacterialcompound, as a lining for refrigerators, freezers or heating cabinets.

JP-A-08145394 and JP-A08145392 describe the use of plasticsincorporating anti-microbial compounds for use in ventilator apparatus.

EP-A-606762 describes a composition of a styrene polymer, anantibacterial agent and a compound having a specific functional group toproduce an antibacterial resin composition.

U.S. Pat. No. 4,533,435 describes an antimicrobial paper for packagingsurgical supplies which incorporates antibacterial compounds in avinylic polymer binding agent.

The incorporation of antimicrobial agents is reviewed by D. Smock inPlastics Formulating and Compounding, March/April 1997 page 16 andPlastics World March 1992 page 58.

The present invention provides a plastics material which has biocidalactivity which is useful in the manufacture of articles having biocidalproperties e.g. for use in food storage and preparation areas or medicalapplications. By “biocidal” we include biostatic activity, i.e. wherethe proliferation of microbiological species is reduced or eliminated inaddition to true biocidal activity where microbiological species arekilled. We also include activity against fungi, bacteria and othermicrobiological species in the meaning of “biocidal”.

According to the invention, we provide a plastics material havingbiocidal activity comprising an acrylic polymeric material and abiocidal compound wherein said acrylic material incorporates from 5% to50% by weight of the total polymer present of a rubbery copolymer.

Preferred biocidal compounds include triclosan, compounds based on heavymetals, especially silver, on inorganic carriers such as zeolites,hydroxyapatite, zinc oxide, titanium dioxide, zirconium phosphate,isothiazolones, benzisothiazolin-3-one derivatives, 10, 10′oxybisphenoxyarsine, isothiazolines, zinc pyrithione, folpet(trichloromethyl thio-phthalimide). Examples of biocidal compounds whichare effective in the invention include those sold under the trademarksDENSIL™ S (2,3,5,6 tetrachloro-4(methyl sulphonyl)pyridine availablefrom Zeneca Ltd), SK-NOB-Z™ (a silver-containing zirconium phosphateavailable from Sanai of Japan) and VANQUISH™ (n-butyl1,2-benzisothiazoline available from Zeneca Ltd). The present inventionis directed towards improving the biocidal activity of acrylic materialscontaining known biocidal compounds and not to the biocidal compoundsthemselves and so it is envisaged that biocidal compounds other thanthose listed above may also be effectively used in the acrylic materialsof the invention. The selection of any particular biocide for articlesof the invention must be made with due regard to the end-use of thearticle and to the particular properties of the biocide, i.e. itsactivity against certain types of micro-organisms, toxicity,processability etc. It is not within the teaching of this document toprovide guidance on the suitability of any one biocidal compound for anyparticular end-use.

The biocide is preferably present at a concentration of at least 0.25%by weight, more preferably at least 1% by weight of the polymer, e.g.0.5-3% by weight.

The acrylic polymeric material comprises a homopolymer or copolymer ofat least one C₁₋₆ alkyl (C₀₋₈alk)acrylate. Preferred acrylic materialsare homopolymers or copolymers of the methyl, ethyl, butyl,2-ethylhexyl, cyclohexyl or phenyl esters of acrylic acid or methacrylicacid. One example of a preferred acrylic material comprises ahomopolymer or copolymer of methyl methacrylate a copolymer comprising80-100% of methyl methacrylate residues and 0-20% of a comonomer of afurther acrylate or methacrylate selected from those materials listedabove.

The composition of the acrylic material is selected according to theapplication in which the material is to be used. For example, if theplastics material is intended to be extruded into a sheet for subsequentthermoforming, e.g. to form a lining for a refrigerated cabinet, then anacrylic material formulated for thermal moulding should be selected.Such acrylic materials may advantageously be copolymers of methylmethacrylate with a minor amount (e.g. 1-20 % wt) of an alkyl acrylate,e.g. methyl, ethyl or butyl acrylate and having a molecular weight ofless than 500,000. For example a suitable copolymer is derived fromabout 90% methyl methacrylate and about 10% of ethyl acrylate having aweight average molecular weight of about 80,000-120,000. The acrylicplastics material may be used as a coating over a base material whichmay be another polymer, such as another acrylic layer, PVC or a styrenebased polymer for example. Acrylic materials have good weathering andchemical resistance as well as providing a high gloss finish andtherefore a coating of acrylic having these properties may be providedto impart a suitable surface finish to another article. The acrylicpolymer may contain additives such as fillers, colorants, impactmodifiers, matting agents etc.

The acrylic material incorporates from 5% to 50% by weight of the totalpolymer present of a rubbery copolymer. By a rubbery copolymer, we meanmaterials which have a glass transition temperature which is less thanroom temperature, preferably less than 0° C., e.g. less than −20° C. Wealso incide block copolymers which include a rubbery, low T_(g) block,often with harder, higher T_(g) blocks. Such materials are well knownfor use as toughening agents for improving the impact resistance ofacrylic materials. Suitable rubbery copolymers include copolymers ofacrylates, methacrylates, styrene, acrylonitrile and/or olefins(especially butadiene). Examples of suitable materials includestyrene—butadiene rubbers, such as the Cariflex™ polymers supplied byShell, styrene-olefin copolymers such as styrene ethylene-butylenestyrene (optionally containing succinic anhydride), styrene-ethylenepropylene, e.g. the polymers sold under the Kraton trademark by Shell,methacrylate-butadiene-styrene (MBS) terpolymers, styrene-acrylonitrilecopolymers, e.g. acrylonitrile-butadiene-styrene (ABS) terpolymers andcore-shell type particles based on alkyl acrylates, e.g. butyl acrylateand styrene. Preferred types of rubbery copolymer include copolymers ofstyrene, butadiene and a methacrylate compound, e.g. MBS copolymers. Wehave found that the incorporation of such rubbery materials enhances thebiocidal effect of biocidal compounds incorporated into the acrylicmaterials. Preferably the plastics material comprises 15-50% by weightof rubbery polymer, especially 20-45%.

Suitable core-shell particles are discrete particles made by multi-stagegraft copolymerisation normally by emulsion polymerisation techniques,each having a multi-layer structure and generally used to improve theimpact resistance of polymers such as acrylic materials. A wide varietyof these particles is available which differ in the type of copolymersfrom which they are made and the number and volume of shells presentaround the core. Typically the core is made from a methacrylate homo orcopolymer and the first shell provides the rubbery material having a lowT_(g), typically made from an alkyl acrylate/styrene copolymer. Thisshell is often formulated to provide a rubbery character for impactmodification whilst being matched in refractive index to the acrylicsubstrate into which it is to be incorporated. A preferred type ofcopolymer to form the shell is based on n-butyl acrylate and an aromaticcomonomer, e.g. styrene or a derivative thereof. A second or subsequentshell may also be present. Many suitable core-shell paricles arecommercially available, e.g. IR441 available form Mitsubishi Rayon Co.,and some commercially available grades of acrylic moulding materialsinclude similar materials pre-compounded in to the polymer. One suitablecore-shell particle is described in WO96/37531 and comprises a(meth)acrylic polymer core, a first shell comprising a low Tg polymercomprising 0-25% by weight of a styrenic monomer and 75-100% of anacrylic monomer, the (meth)acrylic monomer being capable of forming ahomopolymer having a Tg in the range −75 to −5° C., the first shellrepresenting at least 65% by volume of the combined volume of the coreand first shell, and optionally a second shell which comprises a second(meth)acrylic polymer which may be the same as or different from thefirst (meth)acrylic polymer and the core and first shell togethercontain from 0.5-1.0% by weight of a graft cross-linker.

The plastics material of the invention may have many applications. It isuseful as a resin for moulding or extrusion applications, e.g. to makedoors or panels for interior or exterior cladding applications etc. Itmay be provided in the form of a sheet material, e.g. for providingwalls, linings etc or which may be suitable for forming into articlessuch as bathtubs e.g. by thermoforming. It may also be useful in theform of a curable resin, e.g. a polymethyl methacrylate resin dissolvedin methyl methacrylate and optionally containing a dispersion offillers, colours and other functional particles for the manufacture ofsinks, worktops, shower trays etc. The plastics material of theinvention may be especially useful as a coating on a substrate. Onebenefit of this form of the invention is that a relatively small amountof the biocidally active plastic may be used to give biocidal functionto the surface of a non-biocidal substrate.

In a second aspect of the invention therefore, we provide a laminatematerial comprising a substrate material in contact with a layer of aplastics material having biocidal activity comprising an acrylicpolymeric material and a biocidal compound wherein said acrylic materialincorporates from 5% to 50% by weight of the total polymer present of arubbery copolymer. The thickness of the biocidal layer relative to thesubstrate may vary widely e.g. from 100% (i.e. equal thickness) to lessthan 1%. Normally the biocidal layer would be relatively thin, e.g. lessthan 50%, preferably less than 20% of the thickness of the substrate.One particular benefit of providing the plastics material havingbiocidal activity as a relatively thin layer on top of a transparentsubstrate, e.g. transparent acrylic material, is that when the biocidallayer is sufficiently thin, a substantially transparent or translucentlaminate material may be produced. This type of material is useful forproducing articles in which a transparent or translucent effect isdesired in combination with biocidal activity at the surface of thematerial. Such applications include material from which internalfittings for refrigerators are made, shelving for food products, showerscreens etc.

The substrate material preferably comprises a thermoplastic materialselected from the group comprising polystyrene and copolymers ofstyrene, acrylic polymers and copolymers, polyvinyl chloride andpolyolefins and copolymers of these materials, e.g.acrylonitrile-styrene-butadiene (ABS). The substrate may containadditives such as fillers, pigments, plasticisers, impact modifiers,stabilisers etc. The biocidal layer may be applied to the substrate bycoextrusion, extrusion coating, or adhesive or heat-and-pressurelamination of a sheet or film of the biocidal plastics material to thesubstrate material.

Of particular interest for the production of transparent materials isthe use of core-shell impact modifier particles as the rubbery copolymerin the biocidal acrylic material or layer. This is because suchcore-shell particles may be formulated to have a refractive index whichis matched to that of the acrylic material and therefore they may beincorporated into transparent grades of acrylic without reducingsignificantly the transparency of the acrylic material. Therefore it ispossible to improve the biocidal effect of biocides incorporated intoacrylic materials by incorporating a core-shell impact modifier whichhas been selected to match the refractive index of the acrylic material.When an acrylic material incorporating a core-shell particle and abiocide is provided as a thin (e.g. less than 200 μm) layer on a thickertransparent layer of acrylic material then the benefits of biocidalactivity may be provided whilst retaining the transparency of theacrylic.

In a further aspect of the invention we provide a method ofmanufacturing a laminate material comprising the steps of extruding aplastics material having biocidal activity comprising an acrylicpolymeric material and a biocidal compound wherein said acrylic materialincorporates from 5% to 50% by weight of the total polymer present of arubbery copolymer on top of a layer of a substrate material. Thesubstrate material preferably comprises a thermoplastic material whichis coextruded with said plastics material having biocidal activity.

The invention will be further described with reference to the followingexamples.

EXAMPLE 1 Comparative

An acrylic plaque was made by compounding together in a twin-screwextruder at 200-220° C. an injection moulding grade of acrylic polymer(Diakon™ LG156 from ICI Acrylics) with 2% of Vanquish™ 100 biocide fromZeneca Specialties. The biocide was added to the polymer melt by meansof a liquid injection system and the resulting mixture was formed into alace which was cut into small chips. A 50 mm (2″)×75 mm (3″)×3 mm testplaque was formed by injection moulding at 220° C. into a mouldpre-heated to 40° C. The sample plaque was then tested for fungalresistance and bacterial growth as described below. The results aregiven in Table 1.

Fungal Resistance

The samples were tested according to ASTM G21-90. Two 25 mm squares werecut from each sample and placed onto minimal salts agar plates. Theplates were inoculated with a mixed fungal suspension containingaspergillus niger, aureobasidium pullulans, chaetomium globosum,gliocladium virens, penicillium funiculosum and then incubated for 28days at 20° C. The samples were then examined for fungal growth andrated as follows: NG (no growth), TG (trace growth) <10% coverage ontest piece, LG (light growth)—10-30% coverage, MG (moderate growth)30-60% coverage, HG (heavy growth) 60% to complete coverage.

Bacterial Growth EXAMPLES 1-10

0.2 ml of a 24 hour suspension of Escherichia coli was placed onto thesurface of a test piece cut from a sample and then covered with amicroscope coverslip. The samples were incubated for 24 hours at 30° C.and then rinsed with 10 ml of sterile saline solution. The bacteria inthe rinse water were then counted using a serial dilution countingmethod in nutrient agar. The control sample was run with the E. colisuspension placed directly onto a sterile petri dish and covered with acoverslip.

EXAMPLES 2-5

Plaques of acrylic material were made and tested as described in Example1, but with the addition of MBS (KANE™ ACE 56, available from Kaneka) atvarying levels at the compounding stage. The results are given in Table1.

EXAMPLES 6-9

Sample plaques containing 35% by weight of MBS and varying levels ofVanquish 100 biocide were made and tested according to the methoddescribed above. The results are given in Table 1.

EXAMPLE 10

A sample plaque containing 35% MBS and 2% Densil™ S biocide from ZenecaSpecialties was made and tested by the method described above. Theresults are given in Table 1.

TABLE 1 Bacterial Fungal Example Wt % MBS Wt % biocide count growthrating 1 0 2.00 2.5 × 10³ HG/HG 2 15 2.00 4.3 × 10³ HG/HG 3 25 2.00 3.4× 10² HG/HG 4 35 2.00   0 × 10¹ NG/NG 5 45 2.00   0 × 10¹ NG/NG 6 351.00 3.0 × 10³ MG/MG 7 35 0.5 9.0 × 10³ HG/HG 8 35 0.25 3.2 × 10⁴ HG/HG9 35 0.00 6.0 × 10⁵ HG/HG 10 35 2.00 6.3 × 10² LG/MG

EXAMPLE 11 Layered Sample by Coextrusion

A mixture containing 63 wt % Diakon™ LG156, 35% MBS polymer and 2%Vanquish™ 100 antibacterial compound was compounded together and formedinto polymer chips as described in Example 1. The resulting acrylicpolymer was then coextruded at a thickness of 50-100 μm onto a a 1 mmthick clear acrylic layer formed from unmodified Diakon™ LG156. Thesample appeared translucent. The bacterial growth tests were performed,as described below, on the side of the sample containing biocidalcompound. The results are shown in Table 2. The ASTM G21-90 Fungalresistance test gave a result of “no growth”.

Bacterial Growth Tests EXAMPLES 11-16

The samples were tested by a modified tile test vs Escherichia coli NCTC8196. Sections of acrylic (50 mm×50 mm) were wiped with isopropylalcohol and then placed in petri dishes. The surface of the acrylicsample was inoculated with 0.1 ml of a culture of the organism in ¼strength Ringers solution. The acrylic was then covered with asterilised glass slide. The samples were maintained at 20° C. +/−1° C.at >90% RH for 72 hours. The surviving organisms were recovered bywashing/swabbing the acrylic and glass surfaces with 10 ml of Tryptonesoya broth containing inactivators. Recoveries were performed at 24, 48and 72 hours. The resulting broth was serially diluted and plate countsusing plate count agar containing inactivators were performed. Plateswere incubated at 37° C. for 48 hours. Glass slides were used forcontrol counts.

EXAMPLE 12 Comparative

A comparative sample containing 2% Vanquish and 98% LG156 was made asdescribed in Example 11 and tested. The ASTM G21-90 Fungal resistancetest gave a result of “moderate growth”

EXAMPLE 13 Comparative

A comparative sample was made by coextruding unmodified LG156 ontounmodified LG156 substrate as described in Example 11. The ASTM G21-90Fungal resistance test gave a result of “moderate growth”.

EXAMPLE 14

A mixture containing 63 wt % Diakon™ LG156, 35% MBS polymer and 2%Irgasan™ DP300 (triclosan supplied by Ciba Speciality Chemicals)antibacterial compound was compounded together and formed into polymerchips and then coextruded and tested as described in Example 11.

EXAMPLE 15 Comparative

A sample containing 2% tridosan and 98% LG156 was made and tested. Theresults are shown in Table 2.

EXAMPLE 16

A mixture containing 63 wt % Diakon™ LG156, 35% of a core-shell impactmodifier based on MMA/butyl acrylate/styrene copolymers and made asdescribed in the example of WO 96/37531, and 2% Vanquish™ 100antibacterial compound was compounded together and formed into polymerchips and then coextruded and tested as described in Example 11. Thecoextruded sample was clear—transparent and very slightly yellow.

TABLE 2 Wt % Wt % log₁₀ E. coli count @ 20° C. Example Rubber rubberBiocide biocide 0 hours 24 hours 48 hours 72 hours glass control — — —5.3 5.72 6.82 6.93 11 MBS 35 Vanquish 2 5.3 1.70 <1 <1 12 (comp) — —Vanquish 2 5.3 5.28 5.40 4.95 13 (comp) — — — — 5.3 5.32 5.48 4.92 14MBS 35 triclosan 2 5.3 4.49 2.54 1.90 15 (comp) — — triclosan 2 5.3 4.304.18 4.30 16* core-shell 35 Vanquish 2 6.38 4.77 3.91 1.9 17* IR441 35Vanquish 2 6.38 4.85 2.92 <1 core-shell *samples 16 and 17 were testedat a different time using a bacterial sample having a different initialcount.

EXAMPLE 17

A mixture containing 63 wt % Diakon™ LG156, 35% of IR441™ which is acore-shell impact modifier (Mitsubishi Rayon Co). and 2% Vanquish™ 100antibacterial compound was compounded together and formed into polymerchips and then coextruded and tested as described in Example 11. Thecoextruded sample was dear—transparent and very slightly yellow.

The samples were tested again for bacterial growth at 35° C. and theresults are shown in Table 3.

EXAMPLE 18

The biocide+acrylic+MBS compound made in Example 11 was re-compoundedand then coextruded onto a clear acrylic substrate. The biocidal growthresults were very similar to those of Example 11, showing that thematerial can withstand two extrusion operations, whilst maintaining itsbiocidal activity.

TABLE 3 Wt % Wt % log₁₀ E. coli count @ 35° C. Example Rubber rubberBiocide biocide 0 hours 24 hours 48 hours 72 hours glass control — — —6.00 7.48 7.70 8.00 11 MBS 35 Vanquish 2 6.00 1.00 — — 12 (comp) — —Vanquish 2 6.00 5.78 5.95 6.00 13 (comp) — — — — 6.00 4.90 5.00 5.48 14*MBS 35 triclosan 2 5.30 1.00 — — 15 (comp)* — — triclosan 2 5.30 3.77 —— 16 core-shell 35 Vanquish 2 6.00 3.78 3.95 2.48 17 IR441 35 Vanquish 26.00 4.60 4.30 3.90 core-shell *samples 14 and 15 were tested at adifferent time using a bacterial sample having a different initialcount.

What is claimed is:
 1. A plastics material having biocidal activitycomprising a melt compounded acrylic polymeric material comprising ahomopolymer of a C₁₋₆alkyl(C₀₋₈alk)acrylate or a copolymer of methylmethacrylate and up to 20% of a comonomer of aC₁₋₆alkyl(C₀₋₈alk)acrylate, and a biocidal compound wherein said acrylicmaterial incorporates from 5% to 50% by weight of the total polymerpresent of a rubbery copolymer.
 2. A plastics material as claimed inclaim 1, wherein said acrylic material incorporates from 25% to 50% byweight of the total polymer present of a rubbery copolymer.
 3. Aplastics material as claimed in claim 1, wherein said biocidal compoundis selected from the group consisting of: triclosan, heavy metalcompounds on inorganic carriers, isothiazolones,benzisothiazolin-3-ones, 10, 10′ oxybisphenoxyarsine, isothiazolines,zinc pyrithione, folpet (trichloromethylthio-phthalimide), and 2,3,5,6tetrachloro-4(methyl sulphonyl)pyridine.
 4. A plastics material asclaimed in claim 1, wherein said biocidal compound comprises at least0.25% by weight of the plastics material.
 5. A plastics material asclaimed claim 1, which is in the form of a thermoformable sheet.
 6. Aplastics material as claimed in claim 1 which is in the form of asurface coating layer supported on a substrate material.
 7. A plasticsmaterial as claimed in claim 1 which is in the form of a curable resincomposition.
 8. A plastics material as claimed in claim 1 which is inthe form of a moulding resin or moulded article.
 9. A plastics materialas claimed in claim 1, wherein the rubbery material comprises acopolymers of an alkyl acrylate with styrene and optionally othercopolymers.
 10. A plastics material as claimed in claim 9, wherein therubbery material is in the form of a core-shell particle.
 11. A laminatematerial comprising a substrate material in contact with a layer of aplastics material having biocidal activity comprising a melt compoundedacrylic polymeric material comprising a homopolymer of aC₁₋₆alkyl(C₀₋₈alk)acrylate or a copolymer of methyl methacrylate and upto 20% of a comonomer of a C₁₋₆alkyl(C₀₋₈alk)acrylate, and a biocidalcompound wherein said acrylic material incorporates from 5% to 50% byweight of the total polymer present of a rubbery copolymer.
 12. Alaminate material as claimed in claim 11, wherein said substratematerial comprises a thermoplastic material selected from the groupcomprising polystyrene and copolymers of styrene, acrylic polymers andcopolymers, polyvinyl chloride and polyolefins.
 13. A method ofmanufacturing a laminate material comprising extruding a plasticsmaterial having biocidal activity comprising a melt compounded acrylicpolymeric material comprising a homopolymer of aC₁₋₆alkyl(C₀₋₈alk)acrylate or a copolymer of methyl methacrylate and upto 20% of a comonomer of a C₁₋₆alkyl(C₀₋₈alk)acrylate, and a biocidalcompound wherein said acrylic material incorporates from 5% to 50% byweight of the total polymer present of a rubbery copolymer.
 14. A methodas claimed in claim 13, wherein said substrate material comprises athermoplastic material which is coextruded with said plastics materialhaving biocidal activity.
 15. A refrigerator part comprising a plasticsmaterial or a laminate material as claimed in claim
 1. 16. Arefrigerator part as claimed in claim 15, in the form of a lining, doorpanel, shelf or storage box.
 17. A building component comprising aplastics material or a laminate material as claim
 1. 18. A plasticcomposition having biocidal activity consisting essentially of a meltcompounded acrylic polymeric material comprising a homopolymer of aC₁₋₆alkyl(C₀₋₈alk)acrylate, or a copolymer of methyl methacrylate and upto 20% of a comonomer of a C₁₋₆alkyl(C₀₋₈alk)acrylate, a biocidalcompound and a rubbery copolymer, wherein said rubbery copolymer ispresent in an amount from 5% to 50% based on the total weight ofpolymeric components.
 19. A plastics material as claimed in claim 3,wherein said biocidal material comprises heavy metal compound onzeolite, hydroxyapatite, zinc oxide, titanium oxide or zirconiumphosphate.
 20. A plastics material as claimed in claim 19, wherein saidheavy metal compound is a silver compound.
 21. A plastics material asclaimed in claim 1, wherein the acrylic polymeric material is saidhomopolymer.
 22. A plastics material as claimed in claim 1, wherein theacrylic polymeric material is poly(methylmethacrylate).
 23. A plasticsmaterial as claimed in claim 1, wherein the acrylic polymeric materialis said copolymer.
 24. A laminate material as claimed in claim 11,wherein the acrylic polymeric material is poly(methylmethacrylate). 25.A laminate material as claimed in claim 11, wherein the acrylicpolymeric material is said copolymer.